I got to play the Fiora update on PBE; she's a lot of fun
Garen is also a fun champion, Meddler mentioned they're only doing slight tweaks, partially in conjunction with fighter item updates. I hope they make his W more interesting, everything else is pretty iconic so I don't think they'll touch it too much (it's only an MF level update, and most of the work on MF was visual anyways)
Darius...I honestly don't play, but curious to see how it turns out.
I'm curious how Skarner 3.0 turns out, odd that they are re-reworking him so soon. Maybe there's hope for the Cassiopeia players?
Mordekaiser is honestly one of the few champions I still don't understand (I know his abilities and stuff, just don't understand his gameplay pattern). Want to see what they do with him
Poppy I'm excited for; kind of like Fiora she's one of those champions I always wanted to be good at but their old kits never really meshed with me. New Fiora is a lot of fun, hoping for some good stuff with Poppy as well.